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Daylight with daylight control systems and skylights

Modified on: Fri, 5 May, 2017 at 12:32 PM

From DIALux evo 6 onwards it is possible for the designer to plan real daylight control systems, skylights and façade elements into his daylight calculation. In the photorealistic visualization the incidence of sunlight and shadows can be seen at a glance and evaluated.

This includes vertical louvre blinds and textile blinds, skylights, foils and prismatic systems. Several light control elements may be placed and configured on top of each other on windows. The daylight quotient and illuminance within the building are defined, depending on the date, the time, the alignment of the building and the sky conditions.

To configure the products a whole new tool is now available for daylight control systems. Here you can set the site of the lighting installation, the motion /status of movement of window fittings, control strategies and the angle. Systems which have already been configured can quite easily be transferred to other windows.

In addition to rectangular roof windows DIALux now simulates domes, skylights and continuous roof lights for which photometric parameters have been measured.

The electronic catalogues of reputable manufacturers for sunshade and daylight control systems are available for selection of products. The catalogue selection can be specially filtered to show suppliers of daylight-relevant products. Alternatively, you can import product data via the open daylight system ODLS - format or the DIALux DDLS format. These contain images and product descriptions and all the technical data required for light calculation. All the calculation results can be viewed in the result overview and in the product documentation. In addition, there is a documentation of the daylight situation and detailed product descriptions. The light control properties can be seen at a glance with the help of the new hemispheric transmission diagram.

General information

From version 6 onwards the influence of skylights can be simulated and taken into consideration in the calculation of daylight scenes. Real, physically measured products are used for which individual catalogues are available. DIALux evo now employs a new calculation procedure which was developed in cooperation with the Frauenhofer Institute for Building Physics. This is different from other light simulations in that the calculation of the daylight control systems is not via ray tracing. The photometric properties of the products are subjected to physical measurement; and the influence of both the daylight situation and of the products on each other is defined algorithmically. Thus a fast and accurate calculation of the whole scene is possible.

Product types

Louvre blinds

Louvre blinds are mobile or fixed daylight control systems which consist of horizontal or vertical ribs. There are systems for use within buildings or on the façade or both. They are mostly used to protect from direct sunlight and to steer indirect light into the interior of the building. They are controlled manually or are set to move automatically according to the sun.

Blinds

Blinds are systems for darkening a room or are used as sun protection. They are mostly used inside buildings, but there are also systems for outdoor applications.

Foils

Foils are placed directly on the window pane. They are used for UV protection, as privacy shields or, if they include microstructures, also have light controlling properties.

Skylights

Light domes or continuous roof lights can be used as skylights in DIALux. Light domes have firmly prescribed dimensions. Continuous roof lights can be scaled within predefined limits. Skylights perforate the shell of the building just like windows. They are automatically adjusted to the incline of the roof and cut into the surface of the roof at right angles. Skylights can be rotated by the user. However, the user must ensure that no further apertures are formed where the skylight adjoins the surface of the roof.

Material for roof windows

In DIALux it is not possible to mount new layers with sun shades and daylight control systems on skylights as with windows. Standard roof windows can however be fitted with additional materials as can windows. So special forms of roof windows, e.g. roof windows in old projects can later be furnished with light control properties.

Prismatic systems

Light directing filters are static systems, not adjustable systems, which can be fitted in the cavity between the glass panels or directly on the window pane. With the aid of specially formed profiles or structures it is possible to direct the sunlight selectively into the interior of the building.

Self-rotating prismatic systems

This special type of light directing filter has a mirrored micro-louvre structure which is rotated according to the alignment of the building and the angle of the roof. The direct incidence of sunlight is thus kept to a minimum. The alignment is set once when the light directing filter is manufactured. This is therefore also a non-dynamic system. The optimal alignment of self-rotating light directing filters is carried out automatically in DIALux. Later adjustment of the rotation by the user is not possible.

Limitations

Calculating with daylight control systems is subject to certain limitations which the designer must take into consideration and to which we would now like to draw your attention:

Calculation time

When calculating with daylight and daylight control systems, the building apertures are divided into small areas. The division takes place according to the situation and depends on the size, the construction and the system used. A light distribution curve is calculated for each of the small areas. So the calculation time is longer for many large windows with many daylight control systems.

Outdoor areas

Calculation is only for the interior of the building. No conclusions can be drawn about the daylight conditions outside. For this reason the sky is shown as black when a ray tracer is used. For calculation the ray tracer uses luminance ( light density) values which cannot be calculated in areas of daylight outside.

Inner courtyards

At present DIALux evo is not able to recognize windows opening onto a courtyard as relevant for daylight. The daylight entering from a courtyard cannot be calculated.

Visualization

Skylights are displayed with highly simplified geometry. The angle at which the ribs are positioned is not shown in the visualization but the photometric calculation is correct.

Standardized skies

Calculation takes place on the basis of standardized skies as described in CIE 110-1994 „Spatial Distribution of Daylight – Luminance distributions of various reference skies“ Overcast sky, partially overcast sky, clear sky. A luminance (light density) is allocated to each point of the sky. The luminance depends on the angle of altitude of the sun, the solar azimuth and the zenith and the azimuth of the sky. The calculation of photometric values using standardized skies may deviate from the actual values on site.

Quantity of sun shade and daylight control systems

Because of the calculation algorithms used is only possible to calculate façade elements up to a thickness of 0.4 m. DIALux evo calculates a maximum of four layers of sunshade and light control systems.

Working with sun shade and daylight control systems

Pre-conditions A prerequisite for planning sun protection and daylight control systems are building apertures such as windows and roof windows as well as at least one light scene with active daylight calculation. Daylight calculation is activated by selecting a sky in the appropriate light scene.

You obtain product data in the form of ODLS files from the manufacturer of the daylight control system. Activating "Load daylight system" opens the file dialogue. After loading an ODLS file you must allocate a product type (louvre blind, blind, foil, prismatic system, material for roof window) to the product you have selected. You can optionally install the electronic catalogue. The catalogue provides a detailed presentation of the product and is of great assistance in searching for products.

Tools

In the mode "Construction" you will find the tool "Façade elements".

Under "Active façade element" you will find a product image, the name of the façade element selected and a manufacturer logo. Via "Select" you can access the façade elements last used, your personal favourites or the catalogues installed. In "Manufacturer" mode you will find the catalogues or the source from which you can obtain the catalogues.

Placing façade elements

To position a facade element you first select a window in CAD by activating "Add façade element".

add a new layer to the window selected. You will find it again under "Layer configuration". Please check the position of the façade element (inside or outside) and the distance from the window pane which is already there.

You can change the order directly with the mouse or by using the two arrows. You can configure up to four layers per window.

Layer properties

Here you can change the properties of the individual layers, e.g. the position of a textile blind or the angle of a louvre blind system. Not all products have position status, e.g. foils. The position status can be entered as a value in percent for whole window pane, as an absolute value in metres, or with the aid of the slide bar.

Calculation

As with artificial light and previous calculation of daylight, calculation is via the buttons "Start calculation" or "Continue calculation".

Outputs

Under output you will find two separate outputs for daylight control systems

Product data sheets

On the product data sheets for sun protection and daylight control systems you will find not only images, a description and the product dimensions but also a hemispheric transmission diagram. Depending on the incidence of light, this shows the transmission of a product in percent. For each configurable product there is a separate diagram depending on the sets of measured data.

Daylight systems

The output "Daylight systems" shows the position and the layer configuration of the individual daylight systems. In the settings on the side you can set the types of daylight in the output.